Prepare the Spaghetti Squash: Preheat your oven to 400°F (200°C). Cut the spaghetti squash in half lengthwise, scoop out the seeds, and brush the insides with olive oil. Place the squash halves cut-side down on a baking sheet and roast for 30-40 minutes, or until tender. Once done, use a fork to scrape out the spaghetti-like strands and set aside. If using shirataki noodles, rinse and drain them thoroughly, then pat dry.

Cook the Meat Sauce: In a large skillet over medium heat, add olive oil and sauté the diced onion until translucent. Add the minced garlic and cook for another minute. Add the ground beef (or sausage) and cook until browned, breaking it apart as it cooks. Drain any excess fat.

Mix in the Sauce: Stir in the marinara sauce, Italian seasoning, salt, and pepper. Let the mixture simmer for 5-7 minutes, allowing the flavors to meld together.

Prepare the Cream Cheese Mixture: In a medium bowl, combine the softened cream cheese and heavy cream. Whisk until smooth and creamy.

Assemble the Casserole: In a large mixing bowl, combine the spaghetti squash strands (or shirataki noodles) with the cream cheese mixture. Stir in the meat sauce and mix until well combined.

Layer and Bake: Transfer the mixture to a greased casserole dish. Top with shredded mozzarella and grated Parmesan cheese. Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly with a light golden crust.

Serve: Garnish with fresh basil or parsley, if desired, and serve hot.